1. Technical Field
The present invention relates to a printing technology that layers a plurality of ink layer formed by applying a photocurable ink on a printing medium, thereby forming an image.
2. Related Art
The apparatus disclosed in JP-A-2006-150788 (below, referred to as “apparatus of the related art”) is an example of a printing apparatus that forms an image on a printing medium using a photocurable ink. The apparatus of the related art has a recording head (corresponding to the “print head” of the invention) and an ultraviolet ray light source (corresponding to the “light radiating section” of the invention) mounted on a carriage that is freely movable in a main scanning direction. In the apparatus of the related art, a photocurable ink is discharged from the recording head onto a printing medium while the carriage moves in the main scanning direction, thereby forming an image and the image is cured while being irradiated with light from the ultraviolet ray light source, thereby fixing the image to the printing medium.
A technology that uses a transparent thermoplastic resin sheet as the printing medium, and manufactures a printed matter deeply drawing worked into a half-cut shape of a beverage commodity container after decoration printing is carried out by a printing apparatus such as the apparatus of the related art is proposed in the related art (refer to JP-A-2008-87246).
In the apparatus of the related art, the ultraviolet ray light source is arranged neighboring the recording head in the main scanning direction and moves integrally with the recording head in the main scanning direction. Therefore, after the ink discharged from the recording head lands on the printing medium, thereby forming the ink dots, the ink dots are irradiated with ultraviolet rays from the ultraviolet ray light source for at most approximately one second and at least 0.1 seconds. Because the time until the ink is cured in this way is short, in particular, in a case of using a medium with a comparatively high chemical resistance, such as a polycarbonate, as the printing medium, a problem arises in which a compatible layer in which the ink and the printing medium melt into one another is not sufficiently formed, and the adhesive force of the ink to the printing medium is weak.
When various processes are carried out on the printing medium subjected to decoration printing in a state where the adhesive force is weak, the ink may have difficulty ion tracking the expansion when the printing medium is expanded due to the processing, and the ink layer may be damaged.